17 __ ...................................................................... can be defined as "A customer proactively agrees to receive further information." Fill in the blank. a. Opt-out b. Opt-down Opt-in d. Opt-up 18. Amount of purchase is related to which digital data to segment customers? a. Communication frequency b. Communication content Transaction data d. Personál data 19. Which of the below given target market strategies means "targeting the whole market"? a.Concentrated Marketing Strategy b. Differentiated Marketing Strategy c. Mass Marketing Strategy d. Undifferentiated Marketing Strategy 20. Marketing messages are delivered in real-time accordin customers' presence based on the technology they are carrying. This is an example for which concept? a.Social location based marketing b. Permission marketing c. Proximity-marketing d.Propensity modelling